Learn about Alpha router port ing from NAT principles

This article mainly describes the principles of NAT and various ADSL Modem and Alpha router port ing. There is not much direct connection to Alpha router port ing, But I have explained many principles, therefore, it will be helpful for you to learn more about port ing of the Alpha router.

NAT principles

NAT stands for "Network Address Translation", which means "Network Address Translation". It is an IETF (Internet Engineering Task Force, Internet Engineering Task Group) standard, allows an entire organization to appear on the Internet with a public IPInternet Protocol. As the name suggests, it is a technology that translates an internal private IP address into a valid IP address.

To put it simply, NAT uses an internal address in the internal network of the LAN. When the internal node needs to communicate with the external network, it can be understood as an exit at the gateway, for example, replace the internal address with a public address, and use it on the external internet). NAT allows multiple computers to share Internet connections, this function solves the shortage of public IP addresses. In this way, you can apply for only one valid IP address to connect the computer in the LAN to the Internet. In this case, NAT shields the internal network, and all Intranet computers are invisible to the public network, while Intranet computer users generally do not realize the existence of NAT.

The internal address mentioned here refers to the private IP address assigned to the node in the internal network. This address can only be used in the internal network and cannot be routed to a network technology, different paths can be forwarded ). Although the internal address can be randomly selected, the following address is usually used: 10.0.0.0 ~ 10.20.255.255, 172.16.0.0 ~ 172.16.255.255, 192.168.0.0 ~ 192.168.255.255. NAT translates the reserved IP addresses that cannot be used on the Internet into valid IP addresses that can be used on the Internet. A global address is a valid IP address. It is an IP address assigned by the NIC Network Information Center or ISP (Network Service Provider). It represents one or more internal addresses, is a globally unified addressable address.

NAT functions are usually integrated into routers, firewalls, ISDN routers, or individual NAT devices. For example, if this function has been added to the Alpha router port ing, the network administrator only needs to set the NAT Function in the router's IOS to shield the internal network. For example, the firewall maps the internal address 192.168.1.1 of the WEB Server to the external address 202.96.23.11, and the external access address 202.96.23.11 is actually access 192.168.1.1. In addition, small enterprises with limited funds can now implement this function through software. Windows 98 SE and Windows 2000 all contain this function.

NAT technology type

There are three types of NAT: Static NAT, dynamic address NAT, and network address-port translation (NAPTPort-Level NAT ). Static NAT is the most simple and easy to implement. Each host in the internal network is permanently mapped to a valid address in the external network. Dynamic Address NAT defines a series of valid addresses in the external network and maps them to the internal network using dynamic allocation. NAPT maps internal addresses to different ports of an IP address of an external network. Based on different needs, the three NAT solutions have their own advantages and disadvantages.

Dynamic Address NAT only converts IP addresses. It allocates a temporary external IP address for each internal IP address, which is mainly used for dialing. Dynamic NAT can also be used for frequent remote connections. When a remote user is connected, the dynamic address NAT will assign an IP address to the user. When the user is disconnected, the IP address will be released for future use. Network Address Port Translation (NAPTNetwork Address Port Translation) is a familiar conversion method. NAPT is widely used in access devices. It can hide Small and Medium networks behind a valid IP address. Unlike Dynamic Address NAT, NAPT maps internal connections to a separate IP address in the external network, and adds a TCP port number selected by the NAT device to the address.

When using NAPT on the Internet, all different information flows seem to come from the same IP address. This advantage is very practical in small office rooms. By applying an IP address from the ISP, multiple connections are connected to the Internet through NAPT. In fact, many SOHO remote access devices support dynamic IP addresses based on PPP. In this way, ISP does not even need to support NAPT, so that multiple internal IP addresses can share the Internet with one external IP address. Although this will cause certain channel congestion, however, considering the reduced ISP Internet access cost and ease of management, NAPT is worthwhile.

Description of port ing of ADSL Modem

If ADSL itself has a routing function, you need to set the corresponding Alpha router port ing in the "Management Interface" of ADSL. The setting method may vary depending on the brand and model of ADSL. We have collected and summarized some common ADSL port ing methods. Please refer to the relevant models for configuration. If the ADSL cat you are using is not within the scope of our summary, please PM to us and we will try to add it as soon as possible.

Description of Alpha router port ing

If you want to access the Internet through ADSL + vro, you need to set the corresponding Alpha router port ing in the vro. The setting method may vary depending on the brand and model of the vro. We have collected and summarized some common ADSL port ing methods. Please refer to the relevant models for configuration. If the router you are using is not within the scope of our summary, ask PM to give it to us and we will try to add it as soon as possible.